The aim of the article was to answer the question whether the higher economic diversification correlated with the higher living standards in OPEC countries between 1975-2000. Diversification was characterised by two indicators: GDP structure and share of crude and refined oil in exports. Five indicators described living standards: health, food, education, accesses to information and the participation of women in social life. The correlation was calculated by the Spearman method and showed that the assumed hypothesis was proved. The significant correlation coefficients between the share of crude and refined oil in exports and individual living standards indicators occurred more frequently than those between GDP structure and individual living standards. The tendency to diversify economic income and improve living standards is noticeable among most OPEC countries